The present invention relates to a resin molding machine, more precisely relates to a resin molding machine, in which workpiece are supplied from a work supplying section to press units to mold, and the molded products are conveyed from the press units to a product accommodating section.
In the resin molding machine, an upper die and a lower die are relatively moved close and away. Workpieces, hereinafter called works, e.g., lead frames for ICs, LSIs, diodes, are mounted on the lower die, then the dies are closed to mold the works with resin.
A conventional resin molding machine is shown in FIG. 12. Works (lead frames on which IC chips have been mounted) are accommodated in a lead frame supplying section 201. Resin tablets are accommodated in a tablet supplying section 202. A prescribed number of the lead frames are supplied onto a table 204 from the lead frame supplying section 201. The number of the lead frames corresponds to the number of molding sections 203 of the molding dies. Prescribed number of the resin tablets are supplied onto a table. The number of the resin tablets corresponds to the number of pots in the molding dies. The lead frames and the resin tablets on the table are picked up and conveyed to the molding dies by a loader (not shown). The lead frames are molded in the dies with the resin. After molding, molded products, which have been ejected from the dies, are picked up and conveyed to a degating section by an unloader 205. Disused resin is removed from the molded products, then the products and the disused resin are separately collected. When the unloader 205 moves in a space between the upper die and the lower die which have been opened, a cleaner 206 of the unloader 205 cleans parting faces of the dies.
In the case of molding another kind of works, the resin molding machine must be wholly stopped so as to change the molding sections 203. And the lead frame supplying section 201 and the resin supplying section 202 must be changed according to the new works. Further, in the case of cleaning the molding sections 203 with melamine resin, exchanging the molding sections 203 due to damage, etc., the resin molding machine must be wholly stopped. To restart the resin molding machine after cleaning or maintenance, it takes about 1-2 hours until the temperature of the molding dies reaches and is fixed at predetermined temperature. So manufacturing efficiency must be lower.
To adjusting amount of products, it is impossible to mold works by using, for example, two molding sections out of four due to unbalanced clamping. Namely, the dies cannot be used partially. In the case of mass production, the molding dies must be large and heavy, so it is difficult to handle the dies and to make the dies with fixed manufacturing accuracy.
Further, the quality of the molded products cannot be fixed in the large dies.
To uniformly mold the works, a resin molding machine was disclosed in Japanese Patent Patent Gazette No. 64-6539. The resin molding machine has a plurality of press units, in each of which dies are capable of molding one or two lead frames in one molding cycle. Namely, the dies can be small and light, further the dies can be manufactured with fixed manufacturing accuracy.
However, in the resin molding machine disclosed in the Japanese Gazette No. 64-6539, the dies are small in size, so a layout of the resin molding machine must be greatly changed when additional press units are attached so as to increase amount of production.
To easily increase and decrease the amount of production, a resin molding machine was disclosed in Japanese Patent Publication Gazette No. 7-32414. In the resin molding machine, a plurality of sets of molding units, each of which can mold, for example, two lead frames, can be respectively detachably set in a base of the molding machine. With this structure, the the amount of production can be adjusted by attaching or detaching the molding units.
However, in the resin molding machine disclosed in the Japanese Gazette No. 7-32414, routes of a loader for supplying lead frames and a loader for collecting molded products are respectively arranged on each side of the molding units, which are connected in series. With this structure, it is difficult to exchange molding sections of the molding units and to repair the molding units. Further, a large area is required when molding units are connected in series for mass production.
In the transfer molding machine shown in FIG. 12, an electric or hydraulic driven clamping mechanism securely clamps the works between the dies so as to prevent resin leakage, and a transfer mechanism equally exerts the resin in each pot so as to mold the works with equal resin pressure. The mechanisms will be explained with reference to FIG. 13. The clamping mechanism vertically moves a movable platen 305, on which a lower die 304 is fixed, by a hydraulic system (not shown). The transfer mechanism, which has a plurality of plungers (not shown) vertically moving in pots in the lower die 304, is provided to the movable platen 305. The movable platen 305 has a plurality of holes 306 in each of which a plunger holder 307 is provided. The plunger holders 307 are respectively held by pressure equalizing units 308. The pressure equalizing units 308 hydraulically equalize resin pressure in each pot. By the pressure equalizing units 308, the works can be equally molded even if the amount of the resin tablets are not equal. The pressure equalizing units 308 are slidably fitted in slide grooves 309A of an attaching plate 309, so the pressure equalizing units 308 can be pulled out toward the front side. The attaching plate 309 is connected to a transfer cylinder 311 and is capable of vertically moving along guide rods 310. The transfer cylinder 311 is vertically moved by a platen cylinder 312.
When the platen cylinder 312 is moved upward, the pressure equalizing units 308, which are attached to the attaching plate 309, is upwardly moved together with the transfer cylinder 311. By this action, the plungers, which are connected to the pressure equalizing units 308, exert melted resin in the pots to send toward cavities.
These days, ICs are highly integrated and manufactured in a total line, in which wire bonding and resin molding are executed, so the resin molding machine is often used in a clean room, e.g., class 1000. In the clean room, air is filtered to removed fine dusts to increase quality of ICs.
However, in the resin molding machine shown in FIG. 13, resin chips or dusts 313 are piled in the vicinity of the plunger holders 307 and on the attaching plate 309 through the holes 306. If the resin dusts 313 invades into the slide grooves 309A, the pressure equalizing units 308 cannot exchanged.
In the case of manually removing the resin dusts 313 by cleaning means, it is difficult or impossible to insert the cleaning means into the transfer mechanism because the supplying section, the press units and the accommodating section are integrally assembled. By the integrated structure, it is also difficult to repair or clean the clamping mechanism and the driving means of the transfer mechanism.
To overhaul the resin molding machine, the resin molding machine must be wholly stopped. In some cases, the whole machine must be carried out from the clean room; it must be installed thereinto after the overhauls. So it is trouble some to carry out and install the machine for the overhaul. Further, it is bad to open the clean room for overhauling the resin molding machine because many dusts or particles enter thereinto.
In the resin molding machine shown in FIG. 12, the works are supplied from one side of the molding die; the molded products are taken out toward the other side thereof. On the other hand, in a conventional resin molding machine shown in FIG. 14, the works and the products are supplied from and taken out toward one side of the molding dies. In FIG. 14, the lead frames are supplied from a lead frame supplying section 401 to a lead frame arranging section 402 to preheat. The resin tablets are supplied from a resin supplying section (a resin cassette) 403 to a rotary table 402a of the lead frame arranging section 402. The resin tablets are held in a holder 403a while carrying. The lead frames and the resin tablets are held and carried from the lead frame arranging section 402 to molding dies 405 by a loader 404. The lead frames are clamped by the molding dies 405, then melted resin is introduced into the dies 405 to mold the lead frames. After molding the lead frames with the resin, the molded products (the molded lead frames) are picked up and carried to a degating section 407 by an unloader 406 to remove disused resin of the products. The molded products, whose disused resin has been removed by the degating section 407, are accommodated in an accommodating section 408.
The loader 404 is moved along a guide shaft 409, in an X-direction, between a supplying position and a setting position; the unloader 406 is moved along the guide shafts 409, in the X-direction, between a pick-up position and a degating position. The loader 404 and the unloader 406 are arranged parallel to the guide shaft 409. The loader 404 and the unloader 406 are capable of moving in a Y-direction, so they can reciprocatively moved toward and moved away from the molding dies 405. By the reciprocative movement of the loader 404 and the unloader 406 in the Y-direction, the loader can supply the works in the dies 405, and the unloader 406 can pick up the molded products there from.
In the resin molding machine shown in FIG. 14, the loader 404 and the unloader 406 can be respectively linearly moved along the guide shaft 409, so the resin molding machine must be elongated in the X-direction. Namely, a large area is required to install the machine. Especially in the case of installing the machine in the clean room, reducing the area for installation are is required.
In the case of using a plurality of the dies 405 for mass production, the length of the machine, in the X-direction, must be longer. One cycle of the resin molding includes the steps of: picking up the molded products by the unloader 406 from the die 405; moving the unloader 406 away from the die 405; cleaning the parting faces of the die 405; and supplying the next works onto the die 405 by the loader 404. These steps will be executed for each die 405, so molding cycle time is long. It is difficult to shorten the molding cycle time.